boost/random/additive_combine.hpp
/* boost random/additive_combine.hpp header file * * Copyright Jens Maurer 2000-2001 * Distributed under the Boost Software License, Version 1.0. (See * accompanying file LICENSE_1_0.txt or copy at * http://www.boost.org/LICENSE_1_0.txt) * * See http://www.boost.org for most recent version including documentation. * * $Id$ * * Revision history * 2001-02-18 moved to individual header files */ #ifndef BOOST_RANDOM_ADDITIVE_COMBINE_HPP #define BOOST_RANDOM_ADDITIVE_COMBINE_HPP #include <istream> #include <iosfwd> #include <algorithm> // for std::min and std::max #include <boost/config.hpp> #include <boost/cstdint.hpp> #include <boost/random/detail/config.hpp> #include <boost/random/detail/operators.hpp> #include <boost/random/detail/seed.hpp> #include <boost/random/linear_congruential.hpp> namespace boost { namespace random { /** * An instantiation of class template @c additive_combine_engine models a * \pseudo_random_number_generator. It combines two multiplicative * \linear_congruential_engine number generators, i.e. those with @c c = 0. * It is described in * * @blockquote * "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, * Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 * @endblockquote * * The template parameters MLCG1 and MLCG2 shall denote two different * \linear_congruential_engine number generators, each with c = 0. Each * invocation returns a random number * X(n) := (MLCG1(n) - MLCG2(n)) mod (m1 - 1), * where m1 denotes the modulus of MLCG1. */ template<class MLCG1, class MLCG2> class additive_combine_engine { public: typedef MLCG1 first_base; typedef MLCG2 second_base; typedef typename MLCG1::result_type result_type; // Required by old Boost.Random concept BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); /** * Returns the smallest value that the generator can produce */ static BOOST_CONSTEXPR result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return 1; } /** * Returns the largest value that the generator can produce */ static BOOST_CONSTEXPR result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return MLCG1::modulus-1; } /** * Constructs an @c additive_combine_engine using the * default constructors of the two base generators. */ additive_combine_engine() : _mlcg1(), _mlcg2() { } /** * Constructs an @c additive_combine_engine, using seed as * the constructor argument for both base generators. */ BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(additive_combine_engine, result_type, seed_arg) { _mlcg1.seed(seed_arg); _mlcg2.seed(seed_arg); } /** * Constructs an @c additive_combine_engine, using seq as * the constructor argument for both base generators. * * @xmlwarning * The semantics of this function are liable to change. * A @c seed_seq is designed to generate all the seeds * in one shot, but this seeds the two base engines * independantly and probably ends up giving the same * sequence to both. * @endxmlwarning */ BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(additive_combine_engine, SeedSeq, seq) { _mlcg1.seed(seq); _mlcg2.seed(seq); } /** * Constructs an @c additive_combine_engine, using * @c seed1 and @c seed2 as the constructor argument to * the first and second base generators, respectively. */ additive_combine_engine(typename MLCG1::result_type seed1, typename MLCG2::result_type seed2) : _mlcg1(seed1), _mlcg2(seed2) { } /** * Contructs an @c additive_combine_engine with * values from the range defined by the input iterators first * and last. first will be modified to point to the element * after the last one used. * * Throws: @c std::invalid_argument if the input range is too small. * * Exception Safety: Basic */ template<class It> additive_combine_engine(It& first, It last) : _mlcg1(first, last), _mlcg2(first, last) { } /** * Seeds an @c additive_combine_engine using the default * seeds of the two base generators. */ void seed() { _mlcg1.seed(); _mlcg2.seed(); } /** * Seeds an @c additive_combine_engine, using @c seed as the * seed for both base generators. */ BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(additive_combine_engine, result_type, seed_arg) { _mlcg1.seed(seed_arg); _mlcg2.seed(seed_arg); } /** * Seeds an @c additive_combine_engine, using @c seq to * seed both base generators. * * See the warning on the corresponding constructor. */ BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(additive_combine_engine, SeedSeq, seq) { _mlcg1.seed(seq); _mlcg2.seed(seq); } /** * Seeds an @c additive_combine generator, using @c seed1 and @c seed2 as * the seeds to the first and second base generators, respectively. */ void seed(typename MLCG1::result_type seed1, typename MLCG2::result_type seed2) { _mlcg1.seed(seed1); _mlcg2.seed(seed2); } /** * Seeds an @c additive_combine_engine with * values from the range defined by the input iterators first * and last. first will be modified to point to the element * after the last one used. * * Throws: @c std::invalid_argument if the input range is too small. * * Exception Safety: Basic */ template<class It> void seed(It& first, It last) { _mlcg1.seed(first, last); _mlcg2.seed(first, last); } /** Returns the next value of the generator. */ result_type operator()() { result_type val1 = _mlcg1(); result_type val2 = _mlcg2(); if(val2 < val1) return val1 - val2; else return val1 - val2 + MLCG1::modulus - 1; } /** Fills a range with random values */ template<class Iter> void generate(Iter first, Iter last) { detail::generate_from_int(*this, first, last); } /** Advances the state of the generator by @c z. */ void discard(boost::uintmax_t z) { _mlcg1.discard(z); _mlcg2.discard(z); } /** * Writes the state of an @c additive_combine_engine to a @c * std::ostream. The textual representation of an @c * additive_combine_engine is the textual representation of * the first base generator followed by the textual representation * of the second base generator. */ BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, additive_combine_engine, r) { os << r._mlcg1 << ' ' << r._mlcg2; return os; } /** * Reads the state of an @c additive_combine_engine from a * @c std::istream. */ BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, additive_combine_engine, r) { is >> r._mlcg1 >> std::ws >> r._mlcg2; return is; } /** * Returns: true iff the two @c additive_combine_engines will * produce the same sequence of values. */ BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(additive_combine_engine, x, y) { return x._mlcg1 == y._mlcg1 && x._mlcg2 == y._mlcg2; } /** * Returns: true iff the two @c additive_combine_engines will * produce different sequences of values. */ BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(additive_combine_engine) private: MLCG1 _mlcg1; MLCG2 _mlcg2; }; #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION template<class MLCG1, class MLCG2> const bool additive_combine_engine<MLCG1, MLCG2>::has_fixed_range; #endif /// \cond show_deprecated /** Provided for backwards compatibility. */ template<class MLCG1, class MLCG2, typename MLCG1::result_type val = 0> class additive_combine : public additive_combine_engine<MLCG1, MLCG2> { typedef additive_combine_engine<MLCG1, MLCG2> base_t; public: typedef typename base_t::result_type result_type; additive_combine() {} template<class T> additive_combine(T& arg) : base_t(arg) {} template<class T> additive_combine(const T& arg) : base_t(arg) {} template<class It> additive_combine(It& first, It last) : base_t(first, last) {} }; /// \endcond /** * The specialization \ecuyer1988 was suggested in * * @blockquote * "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, * Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 * @endblockquote */ typedef additive_combine_engine< linear_congruential_engine<uint32_t, 40014, 0, 2147483563>, linear_congruential_engine<uint32_t, 40692, 0, 2147483399> > ecuyer1988; } // namespace random using random::ecuyer1988; } // namespace boost #endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP